Skip to main content

Full text of "The Morphology And Evolution Of The Apes And Man"

See other formats

LBMUBOIDBA                             25
mediate in character between the brains of lower Mammals and those of the true Lemurs ; and the brains in the Lemurs have genetic affinities to those of the Primates, His conclusions as to the place of the Lemurine brain are based on macroscopic and experimental observation.
The cerebral hemispheres are small. They cover only a small part of the cerebellum behind; and the large olfactory bulbs project from beneath the hemispheres anteriorly in Lemurs, but not in Chiromys. The lateral ventricle has no posterior horn.
The surface of each hemisphere has a few sulci in Lemurs, G-alagos, Pottos and Lorises, but Weber (162) points  out  that it is  richly convoluted   in   the   large Indrisidae.    The central sulcus (C.S.) is absent or very small.    There is a true Sylvian fissure (F.S.) as in the Primates ;    it varies in size, and it may run into the rhinal fissure below.     In Nycticcbiis,   as  in  many  of the Cebidas, the Sylvian fissure tends to pass into the intraparietal sulcus.    In Lemur the frontal lobe has a well-marked   sulcus  rectus   (S.E.),   which   corresponds to the  inferior  frontal sulcus of the higher Primates. The parallel sulcus (P.S.) does not arch over the upper end of the Sylvian fissure, but the Sylvian and parallel sulci are arched over by the lateral or intraparietal sulcus (L-P. S.),    The latter is free from the transverse occipital or post-lateral sulcus (P.-L.S.) ;    but in the higher Primates the intraparietal sulcus frequently runs into the transverse occipital sulcus, which is concurrent with the simian sulcus.
On the mesial aspect of the hemisphere the calcarine sulcus is seen to be Y-shaped (Ca.S.), but part of the Y